The Brain of the Computer System


CPU Core

Holding a pen in his right hand for calculation, holding the instruction set handbook in his left hand, he is the art of top IC technics. He is the miniature set of many calculation and control circuits, but can only execute the instruction listed in the handbook. Because of the high heat when calculating, he usually wears a hat of heat dissipation.


A processor is the core component of a microcomputer device. Essentially, you can think of a processor chip as a collection of functional circuits that accept commands, read data from a specified memory location or wire, perform calculations, and output the results to be written back to memory. Modern computer systems are very complex. In fact, the system usually contains more than one processor, many peripheral devices have their own processors to run the internal firmware. In the whole computer system, we call the main processor used to run the operating system and applications "Central Processing Unit (CPU)", while the other small processors are called "Micro Control Unit (MCU)".

To be able to run multiple programs at the same time, one modern CPU may contain more than one set of processor circuits, each of which is called a "CPU core." In addition, a modern CPU is more like a conference room of various circuit cores, including GPUs, multimedia codecs, encryption and decryption chips, and other complex computational circuits. Therefore, the CPU is usually the most advanced, fastest, and most expensive part of the entire computer system.

Processor and Instruction Set

A processor is the core component of a microcomputer device. Essentially, you can think of a processor chip as a collection of functional circuits, which basically consists of three types of circuits: First, an arithmetic logic unit, such as addition, subtraction, multiplication, and division of numbers. Second, a data processing unit, such as moving data in and out of the device. Third, a flow control unit, which makes the program move to a branch, based on the results of the previous calculations.

There are hundreds of pins outside the processor. The pins contain three kinds of wiring: First, the control signals, by which different signal inputs can select different functional circuits or change the processor's state. Second, the data input and output lines, by which the data needed in the calculation steps are entered, and the result is outputted from them. And third, the memory address lines. They are usually connected to the main memory which is a large space of data. The processor specifies the address where the data to be read or written back in the memory, then the data contents at that address are imported and exported via the data input/output lines mentioned above.

A computer program is a file containing a colleciton of 0 and 1 sequences. Each 0 and 1 sequence is decoded to correspond to the 0 and 1 signals at the pins to drive the processor. It activates the specified circuit to carry out the specified computation, and the definitions of these "0 and 1 sequences" is called the processor's "instruction set". In principle, programs written in the same instruction set should run properly on the processors of the same instruction set, even if the processors are manufactured by different vendors. On the other hand, a program written in a certain instruction set cannot run on a processor of different instruction set. The most popular instruction sets of processors are the X86, ARM, and RISC-V.

Why is CPU so Hot?

We often use the number of transistors to measure the complexity of a chip's circuitry. According to physical principles, anything that passes through an electrical current at room temperature will generate heat and electromagnetic waves. As CPUs continue to improve over the years, even though the transistors are getting smaller and smaller, the number of transistors continues to multiply because of the complexity of the circuitry, roughly doubling every two years, so you can imagine how hot it will get as we stuff more and more of them into a CPU chip of roughly the same size! Decades ago, the first CPUs didn't need any cooling components. Gradually, in the next few years, CPUs had to be fitted with metal heatsinks, and in the next few years, CPUs not only needed heatsinks, but also large fans, and even water-cooling parts in some systems.

See Also